Today Discovery News published an article about research showing how orange clownfish follow the smell of leaves and anemones, presumably to find their way back to the reef anemones they live within.
The researchers recorded how much time each fish spent on either side of a chamber where each side contained water from different sources. This allowed them to measure the fishes' preference for different-smelling water. (Read the details here.)
Above is a video from Jelle Atema of Boston University, who developed the chamber, showing how the experiment works.
He tested a juvenile blue damsel fish with water from its home reef and from a reef 15 miles away. Watch how the fish switches sides when Atema swaps which side carries the familiar water. The fish quickly swims back into its homey water.
The researchers in the study described today observed similar behavior with the clownfish they studied.
I particularly enjoyed reporting on this research because it was such a great example of the scientific method.
The experiments were as simple as a school science fair project in their straightforward comparisons: No particle accelerators or DNA extractions required. But the tests were clever and the results were clean.
What was incredibly striking is just how strong the fishes' preferences were. When presented with beach water, anemone-scented water, or rainforest-leaf-scented water, the fish spent anywhere from 89 to 98 percent of their time in those waters compared with what you might call "unscented" water. When offered water laced with the scent of an unfamiliar tree leaf, all of the fish scooted out of it immediately, spending 100 percent of the time in the neutral water.
This struck me because when I was in college, I took a class in behavioral ecology where we had to try to measure some aspect of guppy behavior for a class project. We were each given a dozen guppies and a wading pool and sent back to our dorm rooms to run an experiment.
Our groups' experiment was to see whether the size of a guppy school affected how fast the guppies found food. We put six little feeding stations (fish flakes floating inside loops made of drinking straws) around the perimeter of the pool and released schools of 1, 2, 4, 6 and 12 fish, and timed how long it took them to find food in the station that was stocked with food (randomly selected by rolling a die).
The problem was, first of all, that we didn't get the experiment done before winter break. So, we decided that I would carry the guppies home on the airplane and do the experiment in my parents' basement. We figured I could just buy a kiddie pool when I got home.
Somehow, it didn't occur to us that NOBODY sold wading pools in December in Colorado.
Then, one of the guppies gave birth and died, so I went to the pet store to replace the guppy with another grownup. Pregnancy might have been a confounding factor anyway.
After borrowing a wading pool from some neighbors, I retreated to the basement for the guppy time trials ... which failed miserably. The fish just swam around. There was no real trend, and I didn't really have time to make sure the guppies got hungry again in between searches, so who knows what they were looking for.
The whole experience (which, I should add, followed a project earlier in the semester for which I chased squirrels around a campus lawn trying to monitor their nut-caching behavior) convinced me that trying to make quantitative measurements of animal behavior was impossible, or at the very least would lead to several decades in graduate school waiting for animals to get hungry again.
So that's why I took note that the Jones' groups fish time trials come out so cleanly... I guess I should have realized that all those animal research journals weren't just reporting on aimless guppy wandering, so there must be better observations to be made. Still, it's great that this group for found such opinionated fishes.
(Video: Jelle Atema, Boston University)
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Posted by: omega watches | June 26, 2009 at 02:33 AM